The present invention relates to polymer compositions containing conductive particles and more particularly to polymer compositions containing metal-based conductive particles and chlorided metal-based conductive particles in such a manner as to render the composition suitable for use as an electrode surface which is to be exposed to an aqueous environment, as an oxidizing source in intimate contact with a conductive material in a battery, or as a convenient source of silver in touch up electroplating systems.
Ink and plastic formulations have been employed in the past as coatings, layers or surfaces on electrode components. Such formulations as for example described in U.S. Pat. No. 4,592,961 (Ehrreich), U.S. Pat. No. 4,371,459 (Nazarenko), and U.S. Pat. No. 4,425,263 (Nazarenko), include highly conductive particles for purposes of imparting conductivity to the polymer based composition without regard to providing the composition with resistance to harsh or potentially degradative environments and without regard to controlling the electroconductivity of the polymer composition against voltage drift or resistance increase, especially in a direct current environment.
The compositions of the invention are particularly useful as electrode components or as coatings on electrode components which are to be exposed to aqueous environments such as in body electrodes, described for example in U.S. Pat. Nos. 3,976,055; 4,257,424; and 3,977,392, and as are otherwise commercially available. By coating an electrode surface with a composition according to the invention at least over the area which is to be exposed to an electroconductive aqueous environment, the electrode may be protected from electrical degradation and may be stabilized as to electroconductivity.
In accordance with the invention there is provided a composition comprising conductive particles and polymeric material selected from the group of polymers, pre-polymers and mixtures thereof wherein at least about 5 percent by weight of the particles included in the composition have been subjected to treatment such that the particles have chloride at least on their surface prior to inclusion in the composition. In application where a liquid ink is desired, the composition may further include a solvent compatible with the polymeric material and the treated particles.
The particles preferably comprise a metal-based material selected from the group of noble metals, noble metal oxides, and mixtures thereof.
The conductive particles subjected to the pre-chloriding treatment are typically either a noble metal or a noble metal oxide, and are typically coated at least on their surfaces with noble metal chloride as a result of the chloriding treatment.
The noble metal particles selected are most preferably silver metal particles and the noble metal oxides selected are most preferably silver oxide particles. The untreated particles included in the composition may be a mixture of noble metal and noble metal oxide, and the chlorided particles may be a mixture of chlorided noble metal particles and chlorided noble metal oxide particles. Preferably the untreated particles included in the composition are either a noble metal or a noble metal oxide and the treated particles are either a chlorided noble metal or a chlorided noble metal oxide. Most preferably the untreated and treated particles have the same noble metal base. And, typically, the untreated and treated particles are both noble metal-based or noble metal oxide based.
Where a composition according to the invention is used as a coating on a non-conductive substrate, the composition includes at least enough noble metal particles as are necessary to render the composition conductive when in a dry state, for example, an ink coated and dried on a non-conductive substrate.
The polymeric material of the composition is preferably selected from the group of polyesters, vinyl chloride copolymers, vinylidene chloride copolymers, polyurethanes, ethylene copolymers, acrylate polymers, acrylate copolymers, and mixtures thereof. The solvent material, if any, of the composition is preferably selected from the group of ketones, esters, and mixtures thereof.
Most preferably the ratio of chlorided particles to untreated conductive particles included in the composition is selected such that the composition is or remains conductive.
Also in accordance with the invention there is provided a product comprising a composition according to the invention coated on a substrate. The substrate is a dimensionally stable material which is typically non-conductive but may also be conductive. Such coatings are typically accomplished by coating an ink composition according to the invention on a substrate and evaporating any solvent from the coating, e.g., by heating, air drying, or the like. Such coatings may be selectively coated on a suitable substrate in any desired pattern, e.g., in a predetermined printed circuit-like pattern.
Further in accordance with the invention, there is provided a process for making a conductive polymer composition comprising selecting a suitable polymeric material, selecting a suitable metal-based particle material, selecting a suitable metal-based particle material for chloriding, pre-chloriding the selected metal-based particle material, admixing the polymeric material, the metal-based particles and the pre-chlorided metal-based particles, and optionally admixing a compatible solvent.
Further in accordance with the invention, there is provided a process for making a coated product comprising selecting a suitable substrate, selecting a metal-based particle material, subjecting the metal-based particle material to a pre-chloriding treatment such that the particles have metal chloride at least on their surfaces, forming a homogeneous solution comprising the selected polymeric material and a suitable solvent, admixing the treated particles therewith to form a homogeneous solution of the polymeric material and the treated particles, admixing a noble metal particle material with the solution at least when the selected substrate is nonconductive, optionally admixing a noble metal particle material with the solution when the selected substrate is conductive, coating the admixed solution on the the substrate in a predetermined pattern or otherwise, and evaporating the solvent from the coating on the substrate.